Chandra Announcement: CIAO 4.16, CALDB 4.11, DS9 8.5, MARX 5.5.3 released

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Tara Gokas

Dec 12, 2023, 2:57:11 PM12/12/23
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CIAO 4.16, CALDB 4.11, DS9 8.5, MARX 5.5.3 released 

The Chandra X-ray Center (CXC) is pleased to announce that version 4.16 of CIAO ("Chandra Interactive Analysis of Observations") and version 4.11.0 of Chandra CALDB ("Calibration Database") are available for download from .

CIAO 4.16 includes version 8.5 of SAOImage DS9 (the astronomical imaging and data visualization application). DS9 can also be downloaded and installed as a stand-alone application from

Version 5.5.3 of MARX (the Chandra on-orbit performance simulator) can be installed as part of the CIAO installation or separately from

CIAO 4.16 

Notable changes and improvements (read the complete release notes for full details):

  • CIAO 4.16 is now available as native binaries for Apple silicon: M1, M2, M3 ARM processors. (Rosetta2 is no longer required.)

  • CIAO can be installed using the conda package manager. Users can install the conda edition with Python 3.11, 3.10, or 3.9 on Linux and Mac.
    Alternatively, the updated ciao-install script can be used.

  • Several tools have been updated including important bug fixes and enhancements such as:

    • tgextract and mkgrmf have been updated to correct errors with abs(order)>1

    • acis_process_events has been updated to support additional temperature dependent CTI corrections.

    • wcs_match has been updated to to support stacks and range syntax when manually selecting sources.

    • Several tools, including dmextract, have been updated to copy the WCS from the input image to the output table.

Contributed Scripts

Package 4.16.0 incorporates various new scripts and significant updates (read the Analysis Scripts release notes for full details), including: 


Sherpa in CIAO 4.16 incorporates changes in standalone versions Sherpa 4.15.1 and Sherpa 4.16.0  - including 

  • Updated XSPEC models to version 12.13.1e

  • The grouping commands like group_counts now default to only grouping within the noticed range of channels

  • Added support for using arbitrary Python functions when linking model parameter values

  • Support of XSPEC table models with the ESCALE parameter and fix for an issue with models that support a redshift parameter

  • Experimental: support for writing out XSPEC table models

  • Experimental: added support for plotting using bokeh (not included with CIAO; users need to install separately).

Sherpa is also available as a stand alone system, accessible from the Sherpa GitHub repository or from the standalone Sherpa page.

Platform Support

CIAO 4.16 is available for the following platforms (see also the Platform Support Page):

  • 64-bit Linux distributions, built on RedHat Enterprise 8 machine and tested on Ubuntu 20.04LTS

  • macOS Intel x86 and Apple ARM (M1/M2/M3 chips) BigSur (11) through Sonoma (14).

CALDB 4.11.0

Chandra Calibration Database (CALDB) version 4.11.0 is an upgrade to the Chandra CalDB, which includes the following items:

NOTE: CalDB 4.11.0 is only compatible with CIAO 4.16 or later versions. 

To understand if this CALDB upgrade affects your current analysis check: "How CalDB 4.11.0 Affects Your Analysis

SAOImage DS9 v8.5

Version 8.5 of SAOImage DS9 includes:

  • Internal SAMP hub allows DS9 to communicate directly with other SAMP enabled applications and websites without the need of a third party application.

  • Added a new XPA command to get counts in a region.

  • Users can now adjust plot symbol sizes.

For a complete list of changes see the SAOImageDS9 version 8.5 Release Notes page.

MARX 5.5.3

The MARX 5.5.3 release ( is identical to the previous version 5.5.2, except for tweaks in the installation scripts, which contain modifications to ease compiling MARX on Apple systems with M1 or M2 chips.

As always please send questions and requests for enhancements to the CXC HELPDESK

CIAO, CALDB and DS9 are a collaborative effort between the SAO/CXC Science Data Systems group, the SAO/CXC Data System Division, and MIT/CXC personnel.  MARX is created and maintained by the MIT/CXC/HETG group.

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